Conventionally, a developing cartridge is capable of being attached to an image forming apparatus such as a laser printer is known. One conventional developing cartridge accommodates developer therein. The developing cartridge includes an electrode for receiving electric power from the image forming apparatus. The electrode can supply a developing roller with the received electric power from the image forming apparatus. The developing cartridge also includes a coupling. The coupling is configured to receive driving force from the image forming apparatus. The one conventional developing cartridge further includes a detection gear. The detection gear is a gear for transmit, to the image forming apparatus, information representing one or more of specifications of the developing cartridge or information representing as to whether the developing cartridge is a new developing cartridge or not. After the developing cartridge is attached to the image forming apparatus, the coupling receives the driving force from the image forming apparatus, and then, the detection gear can rotate.
Another conventional developing cartridge includes a storage medium (e.g., IC chip). The storage medium can store information representing, for example, a number of printing pages. The another developing cartridge includes a cartridge-side electrical contact portion provided at a contact portion of the detection gear.